Cardio-respiratory adjustments and cost of locomotion in school children during backpack walking (the Italian Backpack Study)

The use of a school backpack is one of the possible causes of back pain in children. Oxygen consumption ( ), pulmonary ventilation, and heart rate (f _c) were measured in 35 pre-pubertal subjects [17 girls and 18 boys, mean (SD) age 11.3 (0.6) years]. They took part in a four-step experiment: (1) standing for 5 min, (2) walking at 3 km·h^–1 for 7 min, (3) walking at 3 km·h^–1 for 7 min carrying a school backpack weighing 8 kg, and (4) walking at 7 km·h^–1 for 5 min with no load. The occurrence of back pain in the last 2–3 years and during the last 15 days was assessed for the subjects by means of a questionnaire. Mean (SD) standing was 215 (45) ml^.min^–1 during walking at 3 km·h^–1, 503 (101) ml^.min^–1 during walking without a load, and increased to 541 (98) ml^.min^–1 during walking with a load (P<0.01). Carrying a backpack increased f _c only minimally. The energy cost of walking at 3 km^.h^–1 without the backpack was 10.0 (2.0) ml O₂ ^.m^–1, and with the backpack was 10.8 (1.9) ml O₂ ^.m^–1 (P<0.01). The net energy cost of locomotion was 0.129 (0.032) ml^.kg body mass^–1.m^–1 for the unloaded condition and slightly lower, at 0.123 (0.025) ml^.kg body mass^–1.m^–1 during loaded walking (P<0.05). Ventilation did not change significantly between unloaded and loaded conditions. When the data were assessed according to the occurrence of back pain, the f _c/ slope was significantly lower in children without back pain, even though the net energy cost of locomotion was similar. Overall, these data suggest that the cardiovascular effortrequired for locomotion while carrying a backpack is minimal. However, fatigability and back pain are more likely to take place in less physical performing subjects. Thus, the occurrence of back pain in schoolchildren during locomotion while carrying a backpack may improve with an improvement in their level of fitness. Electronic Publication     

Modulation of soleus <Emphasis Type="Italic">H</Emphasis>-reflexes during gait in healthy children

During locomotion spinal short latency reflexes are rhythmically modulated and depressed compared to rest. In adults this modulation is severely disturbed after bilateral spinal lesions indicating a role for supra-spinal control. Soleus reflex amplitudes are large in the stance phase and suppressed in the swing phase contributing to the reciprocal muscle activation pattern required for walking. In early childhood the EMG pattern during gait underlies an age-dependent process changing from co-contraction of agonists and antagonists to a reciprocal pattern at the age of 5–7 years. It is unknown whether at this stage apart from the EMG also reflexes are modulated, and if so, whether the reflex modulation is fully mature or still underlies an age-dependent development. This may give important information about the maturation of CNS structures involved in gait control. Soleus Hoffmann H-reflexes were investigated in 36 healthy children aged 7–16 years during treadmill walking at 1.2 km/h and 3.0 km/h. At 7 years old a rhythmic modulation similar to adults was observed. The H-reflex size during the stance phase decreased significantly with age while the maximum H-reflex (H _max) at rest remained unchanged. At 3.0 km/h H-reflexes were significantly larger during the stance phase and smaller during the swing phase as compared to 1.2 km/h but the age-dependent suppression was observed at both walking velocities. In conclusion H-reflex modulation during gait is already present in young children but still underlies an age-dependent process independent of the walking velocity. The finding that the rhythmic part of the modulation is already present at the age of 7 years may indicate that the supra-spinal structures involved mature earlier than those involved in the tonic reflex depression. This may reflect an increasing supra-spinal control of spinal reflexes under functional conditions with maturation.     

Energy cost of treadmill and floor walking at self-selected paces

Summary Oxygen uptake-velocity regression equations were developed for floor and level treadmill walking by having two groups of men, aged 19–29 years (n=20) and 55–66 years (n=22), walk at four self-selected paces, from “rather slowly” to “as fast as possible”. A two-variable quadratric model relating VO₂ (ml·kg⁻¹·min⁻¹) to velocity (m·s⁻¹) was adopted for prediction purposes. However, age and fatness significantly (p<0.05) interacted with treadmill walking speed, while age alone significantly interacted with floor speed. In addition, a significant difference was found between the energy cost of floor and treadmill walking. For example at the normal walking speed of 1.33 m·s⁻¹, the energy cost for the treadmill (age 55–66 years) was 10.58 ml·kg⁻¹·min⁻¹ and for the floor, 11.04 ml·kg⁻¹·min⁻¹ (p<0.05). Four quadratic equations are therefore presented, one each for floor and treadmill in each of the two age-groups. The percent variance explained was between 87 and 95% for each of these equations. Supported by a grant from the Ontario Ministry of Health (DM449)     

The effect of menarcheal age on anthropometric,limb length,and bone measures in Hutterite and non‐Hutterite women

The age women reach menarche may affect bone length and mass. Some studies show an earlier menarcheal age (MA) results in a shorter stature and increased body fat. We hypothesized that Hutterite women have a shorter height and limb length, but greater bone mass and areal bone mineral density (aBMD) than non‐Hutterites. Results are from a secondary analysis of 344 (198 Hutterite) healthy, pre‐menopausal women aged 20?40 years who participated in the South Dakota Rural Bone Health Study. Bone measures were obtained by DXA (spine, hip and total body) and pQCT (4 and 20% distal radius). MA correlated with year of birth (r = ?0.10, P = 0.08) indicating a trend toward a younger MA for women born in more recent years. MA was inversely associated with current weight (r = ?0.11, P < 0.05), percent body fat (r = ?0.16, P < 0.01), femoral neck BMC (r = ?0.18, P = 0.003), femoral neck aBMD (r = ?0.21, P < 0.001), hip aBMD (r = ?0.22, P < 0.001) and trabecular volumetric BMD (vBMD) (r = ?0.14, P = 0.03). Hutterite women had a younger MA than non‐Hutterite women (12.3 ± 1.3 vs. 13.0 ± 1.3 yr, P < 0.001). In final regression models controlling for diet and activity patterns, Hutterite compared to non‐Hutterite women had shorter standing height (162 ± 0.4 vs. 166 ± 0.4 cm, P < 0.001), forearm length (258 ± 0.8 vs. 261 ± 0.9 mm, P = 0.04); and leg length (76 ± 0.2 vs. 77 ± 0.3 cm, P < 0.01) as hypothesized, but MA did not predict these outcomes. In conclusion, younger MA in Hutterite women did not explain their shorter standing height and limb lengths, but total hip aBMD was inversely associated with MA and greater in Hutterite than non‐Hutterite women. Am. J. Hum. Biol., 2008. © 2008 Wiley‐Liss, Inc.     

Bone status in elite male runners

The aim of our study was to compare long distance runners to body mass index (BMI)- and age-matched healthy controls with respect to bone parameters at all relevant loaded and nonloaded skeletal sites. Furthermore, we assessed the effect of running volume on bone parameters. Twenty elite male runners (21.1 km<1:15 h; volume >75 km/week/year) participated in the study (RG), 11 age- and BMI-matched male subjects (28±5 years) served as nontraining controls (CG). Subjects with any medication or illness affecting bone metabolism or with a family history of osteoporosis were not included. Bone parameters at various sites (total body, lumbar spine, femoral neck/hip, calcaneus) were measured by dual energy X-ray (DXA), quantitative computed tomography and quantitative ultrasound. Body composition was assessed via DXA and bioimpedance analysis; nutritional parameters were determined by 5-day dietary protocols. Training variables were assessed by questionnaires. Compared with nontraining controls runners had significantly higher BMD at all loaded sites (calcaneus, lower limbs, femoral neck, pelvis, and trabecular lumbar spine). BMD at nonloaded sites (ribs, upper limbs, and skull) was slightly but not significantly higher in the runners. We observed a low (r=0.30), nonsignificant association between training volume (km/week/year) and trabecular BMD of the femoral neck, which disappeared after adjusting for age, BMI, and body fat in this group of highly trained male runners. The effect of long distance running per se on bone parameters is not deleterious.     

Effects of a daily school based physical activity intervention program on muscle development in prepubertal girls

This 12-month prospective controlled intervention evaluated the effect of a general school based physical activity program on muscle strength, physical performance and body composition in prepubertal girls. Fifty-three girls aged 7–9 years involved in a school based exercise program [40 min/day of general physical activity per school day (200 min/week)] were compared with 50 age-matched girls who participated in the general Swedish physical education curriculum (mean 60 min/week). Body composition (DXA), isokinetic peak torque (PT) of the knee extensors and flexors at 60 and 180°/s, and vertical jump height (VJH) were assessed at baseline and 12 months. The annual gain in weight was similar between the groups, but there was a greater increase in total body and regional lean mass (P < 0.05) and fat mass (P < 0.01) in the exercise group. Mean gains in knee extensor PT at 60 and 180°/s were 7.0–7.6% greater in the exercise group (P ranging <0.05–<0.001). No significant differences were detected in VJH. In conclusion, increasing school based physical education to at least 3 h/week provides a feasible strategy to enhance the development of muscle strength and lean mass in prepubertal girls.     

Exercise-induced breathing patterns of youth are related to age and intensity

The influences of sex, age, exercise intensity, and end-tidal CO₂ on the inspiratory drive ([V _T kg⁻¹]·T _i ⁻¹) and respiratory timing (T _i·T _tot ⁻¹) components of ventilation were examined in 295 youth (138 females, 157 males); similarly distributed 8–18 years of age. Ventilatory and metabolic measures were collected breath-by-breath at rest and during a slow walk (4.0 km h⁻¹), fast walk (5.6 km h⁻¹) and run (8.0 km h⁻¹). Regression modeling for drive (age, sex, and P_ETCO₂) found that sex was significant (R ² < 0.017; P < 0.05) for rest and running, but not walking. Compared to rest, drive increased by 120% for the slow walk, 217% for the fast walk and 258% for the run (P < 0.0001). Drive decreased with age (P < 0.0001): rest = 0.41 ml kg⁻¹ s⁻¹ year⁻¹; slow walk = 0.90 ml kg⁻¹ s⁻¹ year⁻¹; fast walk = 1.30 ml kg⁻¹ s⁻¹ year⁻¹; and run = 1.47 ml kg⁻¹ s⁻¹ year⁻¹. In the regression models for timing, sex provided ∼ 1% of the variance during the run, but was not significant during rest or walking. Timing increased with exercise intensity by approximately 0.02 units (P < 0.001), but decreased by ∼ 0.002 units year⁻¹ with age for all conditions (P < 0.003). Changes in drive and timing were marginally related to end-tidal CO₂ (exercise R ² < 0.063 for all models). These results suggest that in the control of inspiratory drive and timing during exercise in youth, sex is of minor importance but there are age-related changes which are marginally associated with CO₂.     

Three-month bilateral hopping intervention is ineffective in initiating bone biomarker response in healthy elderly men

In animal studies, bone adaptation has been initiated successfully without the transient force spike associated with high impact exercises. Consequently, a 12-week bilateral hopping on the balls of the feet intervention was conducted. 25 elderly men (age 72(SD4) years, height 171(6) cm, weight 75(9) kg) were randomly assigned into exercise and control groups. Ten subjects in each group completed the study. Carboxyterminal propeptide of type I collagen (CICP), bone-specific alkaline phosphatase (bALP) and carboxyterminal telopeptide of type I collagen (CTx) were measured from venous blood samples at baseline, at 2 weeks and at the end of the intervention. Maximal ground reaction force (GRF), osteogenic index (OI) and jump height (JH) were determined from bilateral hopping test and balance was assessed with velocity of center of pressure (COP_velocity) while standing on the preferred leg with eyes open. The intervention consisted of 5–7 sets of 10 s timed bilateral hopping exercise at 75–90% intensity three times/week. There was no significant group × time interaction for GRF, OI and JH (P = 0.065). GRF (11% change from baseline vs. 4%), OI (15 vs. 6%) and COP_velocity (−10 vs. −1%) were not influenced by the intervention (P > 0.170), while the control group improved JH (P = 0.031) (2 vs. 18%). For the biomarkers, no effect was observed in MANOVA (P = 0.536) or in univariate analyses (P = 0.082 to P = 0.820) (CICP −2 vs. −3%, CTx 8 vs. −12%, bALP 0 vs. −3.7%). Allowing transient impact force spikes may be necessary to initiate a bone response in elderly men as the intervention was ineffective.     

Cortical bone resorption during exercise is interleukin-6 genotype-dependent

The objective of this study was to examine the relationship between the interleukin-6 (IL-6) −174 G>C promoter polymorphism and exercise-induced femoral cortical bone resorption. Skeletal response to exercise was assessed in 130 male Caucasian army recruits. Five cross-sectional magnetic resonance images of the right femur were obtained before and after a 10-week period of basic physical training, and changes in cross-sectional cortical area were calculated. Recruits were genotyped for the −174 G>C IL-6 promoter polymorphism. Genotype frequencies (GG 36%, GC 47%, CC 22 17%) were in Hardy–Weinberg equilibrium. The mean percentage change in proximal femoral cross-sectional cortical area was strongly IL-6 genotype-dependent, with GG homozygotes losing 6.8 (3.82)% in cortical area, GC gaining +5.5 (4.88)% and CC gaining +17.3 (9.46)% ( P =0.007 for linear trend). These changes persisted throughout the right femur and were significant in the femur as a whole ( P =0.03). This study demonstrates an association between a functional polymorphism in the IL-6 gene and femoral cortical remodelling during strenuous physical exercise. Previous studies have suggested an important role for IL-6 in the regulation of bone mass in postmenopausal women, and in the invasion of bone by metastatic tumour deposits. These data extend these observations to the regulation of bone mass in healthy males, supporting a fundamental role for IL-6 in the regulation of bone mass and bone remodelling in humans. Electronic Publication     

Rowing prevents muscle wasting in older men

We evaluated the effects of rowing on the morphology and function of the leg extensor muscle in old people. The area and the power of the leg extensor muscle were measured in 15 oarsmen – age [mean (SD)] 65 (3) years; height 171 (4) cm, body mass 68 (6) kg – and in 15 sedentary men – age 66 (4) years, height 170 (4) cm, body mass 67 (7) kg – who were matched on the basis of their body size. The leg extensor muscle area of the oarsmen was larger than that of the sedentary men [77.8 (5.4) vs 68.4 (5.1) cm², P<0.05]. Also the bilateral leg extension power of the oarsmen was larger than that of the sedentary men [1,624 (217) vs 1,296 (232) W, P<0.05]. Thus, the leg extension power per the leg extensor muscle area was not significantly different between two groups [20.9 (2.0) vs 19.9 (2.1) W·cm^–2) and leg extension power was correlated to the leg extensor muscle area (59–89 cm², r=0.74, P<0.001). Also the 2,000-m rowing ergometer time of the oarsmen [495 (14) s; range 479–520 s] was related to leg extensor muscle area (68–89 cm², r=0.63, P<0.01). The results suggest that rowing prevents age-related muscle wasting and weakness. Electronic Publication     

Menarcheal age in Turkey: Secular trend and socio-demographic correlates

Background: Menarche is an important indicator for assessing the developmental status of pubertal girls. Despite its importance, there is no nationwide information on menarcheal age in Turkey.

Aim: This paper is the first attempt to examine age at menarche for Turkey as a whole. The aim is to present the secular trend of menarcheal age and variations across different socio-demographic groups.

Methods: Data were employed from the Turkey Demographic and Health Survey, 2008. Mean menarcheal ages were estimated for birth cohorts and socio-demographic sub-groups. The pace of decline in menarcheal age has been estimated using multiple linear regression analysis, controlling for year of birth and other variables.

Results: Mean age at menarche was estimated as 13.30 (95% CI = 13.26–13.35). It was estimated as 13.17 years (95% CI 12.95–13.38) for the youngest birth cohort (1989–1993), as opposed to 13.44 (95% CI 13.37–13.52) years for the cohort born in 1959–1968.

Conclusion: Regression analysis indicated a decrease of 1.44 months per decade, providing evidence of a secular trend in menarcheal age in Turkey. Further results suggested childhood place of residence, education, welfare status and number of siblings to be significantly associated with menarcheal age.     

Low agreement of ventilatory threshold between training modes in cardiac patients

In cardiac rehabilitation, different endurance exercises such as walking and cycling are often performed. The training intensity for these modes is determined from a single treadmill or bicycle test by ventilatory threshold (VT). In this study, differences of VT between walking and cycling and agreement of VT between training modes were assessed in cardiac patients. A total of 46 cardiac rehabilitation patients (mean age 59.5 ± 8.4 years, 45 males) (31 untrained and 15 trained) completed a maximal exercise test on bicycle and treadmill, with breath-by-breath analysis of oxygen uptake (VO₂), carbon dioxide production and expiratory volume. VT was determined by V-slope method. Correlations of VT and VO_2peak were calculated between exercise modes. Bland–Altman plots were made for determining VT agreement between modes. VT was significantly different between walking and cycling in trained patients (P < 0.05), but not in untrained patients (P > 0.05). When untrained and trained patients were compared, VT correlation was lower (r = 0.50) in the former group, as compared to the latter group (r = 0.78). Also, Bland–Altman plots showed smaller limits of agreement for VT in trained (2 SD −1.6 to 7.8 ml/min/kg), as compared to untrained patients (2 SD −7.0 to 9.6 ml/min/kg). In trained patients, VT correlates well between training methods, but is highly exercise mode specific. In untrained patients, VT is not exercise mode specific, but the VT has a low correlation between training modes. This study shows that VT should be assessed by the appropriate exercise model for determining exercise intensity in cardiac rehabilitation.     

Maximal isokinetic and isometric muscle strength of major muscle groups related to age,body mass,height, and sex in 178 healthy subjects

The main objective of this study was to establish normative values for maximal concentric isokinetic strength and maximal isometric strength of all major muscle groups in healthy subjects applying sex, age, height, and body mass-adjusted statistical models. One hundred and seventy-eight (178) (93 male and 85 female) healthy non-athletic Danish volunteers aged 15–83 years were recruited. Eighteen test protocols for each sex were applied to determine isokinetic and isometric muscle strength at knee, ankle, hip, shoulder, elbow, and wrist using a dynamometer (Biodex System 3 PRO). Multiple linear regressions were performed with maximal muscle strength (peak torque) as dependent variable and age, height, and body mass as independent variables. Muscle strength significantly related to age in 24, to height in 13 and to body mass in 27 out of the 36 models. In gender-specific analyses, the variables age, height and body mass accounted for 25% (20–29) (95% confidence interval) of the variation (r ²) in strength for men and 31% (25–38) for women. The r ² was similar for the isokinetic models and the isometric models [31% (22–40) vs. 28% (23–34)]. Age, height, and body mass related to strength in most muscle groups and gender-specific models with estimated prediction intervals were established for maximal strength of major muscle groups.     

Prediction of systemic exposure to cyclosporine in Japanese pediatric patients

The monitoring of the blood concentration at 2 h (C₂) after the oral administration of a cyclosporine (CsA) microemulsion was reconfirmed to be useful for the prediction of systemic exposure, the area under the blood concentration–time curve from 0 to 4 h (AUC_0–4), in a group of Japanese patients, consisting of 33 children aged 5–15 years and 19 young adults aged 16–27 years, with a greater correlation for C₂ (r = 0.927) than the trough concentration (r = 0.488). The dose-normalized AUC_0–4 was independent of gender or indications for CsA, while it depended on body size, i.e., the age (P = 0.065) and total body weight (P = 0.026). MDR1 C3435T had a weak, but insignificant effect (P = 0.072); it was about 22–31% lower in the patients with TT³⁴³⁵. Co-administration of a steroid and further treatment with nifedipine had a more intensive effect (P = 0.018); co-administration resulted in a 51% increase in the dose-normalized AUC_0–4. A strong effect was also observed for the serum total cholesterol level (P = 0.001). Collectively, the discrepancies in the results on MDR1 C3435T among investigators might be due to variability in the age/total body weight, co-administration drugs or serum lipid level.     

Effect of a 24-h continuous walking race on cardiac autonomic control

This study investigated the relationships between walking speed and heart rate (HR) variability (HRV) in eleven subjects during a 24-h race. It was hypothesized that the nycthemeral rhythm on HR is preserved during the race. RR intervals and walking speed were measured. Fast Fourier transform was applied to samples of 1,024 successive RR intervals collected every hour from a HR monitor. Walking speed was averaged every hour and decreased (first lap: 8.8 ± 0.3 vs. last lap: 7.3 ± 0.8 km h⁻¹, P < 0.001) with HR also decreasing (max at 19:00 h: 143 ± 9 vs. min at 7:00 h: 117 ± 14 beats min⁻¹, P < 0.001) following a third order polynomial shape. HRV power spectral components followed distribution patterns similar to the mean RR during the race with a minimum in the early evening (19:00–20:00 h) and a maximum in the morning (5:00–8:00 h). Thus, as for mean RR, spectral components over time are also fitted to a third order polynomial regression. LF/HF ratio increased linearly (min = 0.5 ± 0.3, max = 2.8 ± 5.3, P = 0.02). Although mean HF peak did not decrease significantly over time, it was positively correlated with walking speed. In conclusion, this study showed that despite a constant decrease in walking speed, HR circadian rhythm is preserved during a continuous 24-h walking race. The short-term HRV components remain linked to HR whereas the LF/HF ratio increases linearly until the end of the race whatever HR is.     

A continuous decline in menarcheal age in Denmark

We report a renewed decline in mean menarcheal age in a large Danish sample after a period with a halt in the trend towards earlier age at menarche in many North European countries. In our study based on retrospective data from six different samples constituting 42784 women, we find a continuously declining mean menarcheal age in Denmark among women born in the years 1964-1973. In a sample of textile workers born in the years 1939-1968 (n = 12605) we find a 1 year higher mean menarcheal age. This indicates that menarcheal age is still delayed in certain groups in Denmark. This leaves the possibility that the menarcheal age could fall even further in the future.     

Balance and gait in children with dyslexia

Tests of postural stability have provided some evidence of a link between deficits in gross motor skills and developmental dyslexia. The ordinal-level scales used previously, however, have limited measurement sensitivity, and no studies have investigated motor performance during walking in participants with dyslexia. The purpose of this study was to investigate if continuous-scaled measures of standing balance and gait could discriminate between groups of impaired and normal readers when investigators were blind to group membership during testing. Children with dyslexia (n=22) and controls (n=18), aged 10–12 years, performed walking tests at four different speeds (slow–preferred–fast–very fast) on an even and an uneven surface, and tests of unperturbed and perturbed body sway during standing. Body movements were registered by a triaxial accelerometer over the lower trunk, and measures of reaction time, body sway, walking speed, step length and cadence were calculated. Results were controlled for gender differences. Tests of standing balance with eyes closed did not discriminate between groups. All unperturbed standing tests with eyes open showed significant group differences (P<0.05) and classified correctly 70–77.5% of the subjects into their respective groups. Mean walking speed during very fast walking on both flat and uneven surface was ≥0.2 m/s (P≤0.01) faster for controls than for the group with dyslexia. This test classified 77.5% and 85% of the subjects correctly on flat and uneven surface, respectively. Cadence at preferred or very fast speed did not differ statistically between groups, but revealed significant group differences when all subjects were compared at a normalised walking speed (P≤0.04). Very fast walking speed as well as cadence at a normalised speed discriminated better between groups when subjects were walking on an uneven surface compared to a flat floor. Continuous-scaled walking tests performed in field settings may be suitable for motor skill assessment as a component of a screening tool for developmental dyslexia. Electronic Publication     

Postnatal changes in the styloid process,vagina processus styloidei,and stylomastoid foramen in relation to the function of muscles originating from the styloid process

We investigated age-related changes in the styloid process in 88 skulls, aged from 5 months to 85 years of age. The osseous styloid process was not well developed in children. Its length increased significantly with age (from 2.3 mm in 11–20 age group to 16.3 mm in 61–85 group). In adolescent specimens (11–20 years of age), the median distance from the styloid process to the stylomastoid foramen was 0.7–0.8 mm, whereas in adult and old age specimens the two structures were completely adjacent or very close, usually less than 0.2 mm. The process was missing in 5% of the adult specimens. There was a statistically significant positive association between the length of the styloid process with age (r = 0.3210, 95% CI 0.0817–0.5254; P = 0.0097), whereas the distance from the styloid process to the stylomastoid foramen significantly decreased with age (r = −0.4518, 95% CI −0.6167 to −0.2490; P = 0.0001). Changes in the length and shape of the styloid process reflected altered function of the three muscles originating from the styloid process—m. stylopharyngeus, m. stylohyoideus and m. styloglossus. They have a common function of lifting the aerodigestive elements upward and backward, after the descent of the aerodigestive tract and final morphological differentiation of the vocal system during puberty. Relationship between altered muscle function and the morphology of the styloid process are important for understanding the clinical syndromes related to the styloid process, such as Eagle’s syndrome. Presented as a poster at the 78 Jahresversammlung 2007 der Deutschen Gesellschaft für Hals-Nasen-Ohren-Heilkunde, Kopf- und Hals-Chirurgie e.V., Munich, 17–20 May 2007.     

Association of maternal menarcheal age with anthropometric dimensions and blood pressure in children from Greater Bilbao

Abstract

Background: Earlier menarche has been related to shorter height and greater obesity-related anthropometric dimensions and blood pressure in women. Boys and girls with earlier maternal menarcheal age (MMA) have shown greater height and body mass index (BMI) in childhood.

Aim: To analyse associations of menarcheal age with their own and their children’s anthropometric dimensions and blood pressure.

Subjects and methods: The sample consisted of 493 women and their children (aged 2–19 years) from Greater Bilbao (Basque Country, Spain). For both generations there is information on 19 anthropometric dimensions, blood pressure and socio-demographic characteristics. Linear regressions adjusted for different covariates were used to analyse the associations.

Results: Menarcheal age in women showed the greatest positive associations with iliospinal height and ectomorphy and negative associations with BMI, sum of six skin-folds, endomorphy and mesomorphy. Boys with earlier MMA had greater body heights and breadths, particularly iliospinal height and biacromial breadth (0.10?z-score/year; p?<?0.05). In girls, earlier MMA predicted greater sitting height, biepicondylar humerus breadth, weight and sum of four circumferences (0.07–0.09?z-score/year; p?<?0.05). However, there was some evidence that MMA was positively associated with body heights, ectomorphy and blood pressure in girls aged ≥12.

Conclusion: Children with earlier MMA tend to have greater anthropometric dimensions. Adolescent growth spurt might affect these relationships, at least in girls.     

Effects of age and gender on the propelling efficiency of the arm stroke

The propelling efficiency of the arm stroke (η _P) was estimated in a group of 63 male and female subjects (9–59 years of age) of good technical skill, swimming the front crawl at sub-maximal speeds. η _P was calculated on the basis of values of speed (v), stroke frequency (SF) and shoulder-to-hand distance (l, calculated from measures of arm length and elbow angle during the in-sweep) as proposed by Zamparo et al. (Eur J Appl Physiol 94:134–144, 2005). In both genders, the distance covered per stroke (Ds = v/SF) is similar before puberty, reaches its maximum at about 20 years of age and then steadily declines. l is significantly larger in males than in females and this difference tended to offset the differences in Ds so that η _P is almost the same in male and female swimmers of the same age group and swimming ability: about 0.31 before puberty, 0.38–0.40 at about 20 years of age and about 0.25 in swimmers older than 40 years of age. The development of η _P and Ds during the life span is similar to the changes in muscle strength and power reported in the literature suggesting that these parameters are related to the ability to exert forceful (and hence effective) strokes in water. Since the energy cost of swimming (C) depends essentially on η _P and the hydrodynamic resistance (W _d), these data further suggest that differences in C between genders are mainly to be attributed to differences in W _d, whereas differences across ages can be attributed also to changes in η _P.